Battery pack with integral cooling and bussing devices

RELATED APPLICATIONS

p-0002This non-provisional application claims priority to provisional application Ser. Nos. 60/851,684 filed on Oct. 13, 2006, and 60/855,787 filed on Nov. 1, 2006, and 60/922,632 filed on Apr. 10, 2007, and incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

p-0003The subject invention relates to battery packs having cells and more particularly, to a battery pack for electric/hybrid vehicles having a cooling system or a heating system for cooling the cells within the battery pack.

BACKGROUND OF THE INVENTION

p-0004Motor vehicles, such as, for example, hybrid vehicles use multiple propulsion systems to provide motive power. This most commonly refers to gasoline-electric hybrid vehicles, which use gasoline (petrol) to power internal-combustion engines (ICEs), and electric batteries to power electric motors. These hybrid vehicles recharge their batteries by capturing kinetic energy via regenerative braking. When cruising or idling, some of the output of the combustion engine is fed to a generator (merely the electric motor(s) running in generator mode), which produces electricity to charge the batteries. This contrasts with all-electric cars which use batteries charged by an external source such as the grid, or a range extending trailer. Nearly all hybrid vehicles still require gasoline as their sole fuel source though diesel and other fuels such as ethanol or plant based oils have also seen occasional use.

p-0005Batteries and cells are important energy storage devices well known in the art. The batteries and cells typically comprise electrodes and an ion conducting electrolyte positioned therebetween. Battery packs that contain lithium ion batteries are increasingly popular with automotive applications and various commercial electronic devices because they are rechargeable and have no memory effect. Storing and operating the lithium ion battery at an optimal operating temperature is very important to allow the battery to maintain a charge for an extended period of time.

p-0006Due to the characteristics of the lithium ion batteries, the battery pack operates within an ambient temperature range of −20° C. to 60° C. However, even when operating within this temperature range, the battery pack may begin to lose its capacity or ability to change or discharge should the ambient temperature fall below 0° C. Depending on the ambient temperature, the life cycle capacity or charge/discharge capability of the battery may be greatly reduced as the temperature strays from 0° C. Nonetheless, it may be unavoidable that the lithium ion battery be used where the ambient temperature falls outside the temperature range.

p-0007Alluding to the above, significant temperature variances can occur from one cell to the next, which is detrimental to performance of the battery pack. To promote long life of the entire battery pack, the cells must be below a desired threshold temperature. To promote pack performance, the differential temperature between the cells in the battery pack should be minimized. However, depending on the thermal path to ambient, different cells will reach different temperatures. Further, for the same reasons, different cells reach different temperatures during the charging process. Accordingly, if one cell is at an increased temperature with respect to the other cells, its charge or discharge efficiency will be different, and, therefore, it may charge or discharge faster than the other cells. This will lead to decline in the performance of the entire pack.

p-0008The art is replete with various designs of the battery packs with cooling systems. The U.S. Pat. No. 5,071,652 to Jones et al. teaches a metal oxide-hydrogen battery including an outer pressure vessel of circular configuration that contains a plurality of circular cell modules disposed in side-by-side relations. Adjacent cell modules are separated by circular heat transfer members that transfer heat from the cell modules to the outer vessel. Each heat transfer member includes a generally flat body or fin which is disposed between adjacent cell modules. A peripheral flange is located in contact with the inner surface of the pressure vessel. The width of each cell module is greater than the length of the flange so that the flange of each heat transfer member is out of contact with the adjacent heat transfer member. The flanges are constructed and arranged to exert an outward radial force against the pressure vessel. Tie bars serve to clamp the cell modules and heat transfer members together in the form of a stack which is inserted into the pressure vessel.

p-0009The metal oxide-hydrogen battery taught by the U.S. Pat. No. 5,071,652 to Jones et al. is designed for cylindrical type of batteries and teaches the heat transfer members in direct contact with the vessel thereby failing to create a clearance between the vessel and the heat transfer members, which can be used to introduce cooling or heating agent to cool or heat the cells.

p-0010The U.S. Pat. No. 5,354,630 to Earl et al. teaches a common pressure vessel of a circular configuration type Ni—H.sub.2 storage battery having an outer pressure vessel that contains a stack of compartments. Each of the compartments includes at least one battery cell, a heat transfer member, and a cell spacer for maintaining a relatively constant distance between adjacent compartments. The heat transfer members include a fin portion, which is in thermal contact with the battery cell, and a flange portion which extends longitudinally from the fin portion and is in tight thermal contact with the inner wall of the pressure vessel. The heat transfer member serves to transfer heat generated from a battery cell radially to the pressure vessel.

p-0011Similarly to the metal oxide-hydrogen battery taught by the U.S. Pat. No. 5,071,652 to Jones et al., the storage battery taught by the U.S. Pat. No. 5,354,630 to Earl et al. is designed for cylindrical type of batteries. This metal oxide-hydrogen battery teaches the heat transfer members being in direct contact with the vessel thereby failing to create a clearance between the vessel and the heat transfer members which can be used to introduce cooling or heating agent to cool or heat the cells.

p-0012The U.S. Pat. No. 6,117,584 to Hoffman et al. teaches a thermal conductor for use with an electrochemical energy storage device. The thermal conductor is attached to one or both of the anode and cathode contacts of an electrochemical cell. A resilient portion of the conductor varies in height or position to maintain contact between the conductor and an adjacent wall structure of a containment vessel in response to relative movement between the conductor and the wall structure. The thermal conductor conducts current into and out of the electrochemical cell and conducts thermal energy between the electrochemical cell and thermally conductive and electrically resistive material disposed between the conductor and the wall structure. The thermal conductor taught by the U.S. Pat. No. 6,117,584 to Hoffman et al. is attached to one or both of the anode and cathode contacts of the cell and not between the cells.

p-0013The U.S. Pat. No. 6,709,783 to Ogata et al. teaches a battery pack having a plurality of prismatic flat battery modules constituted by nickel metal hydride batteries, arranged parallel to each other. Each battery module consists of an integral case formed by mutually integrally connecting a plurality of prismatic battery cases having short side faces and long side faces, the short side faces constituting partitions between adjacent battery cases and being shared. A plurality spacers are made of a sheet bent in opposite directions such that alternately protruding grooves or ridges respectively contact the opposite long side faces of the battery modules for providing cooling passages between the battery modules. The battery pack taught by the U.S. Pat. No. 6,709,783 to Ogata et al. is intended to define voids, i.e. the cooling passages between the cells thereby diminishing the packaging characteristics of the pack.

p-0014The U.S. Pat. No. 6,821,671 to Hinton et al. teaches an apparatus for cooling battery cells. As shown in FIG. 1 of the U.S. Pat. No. 6,821,671 to Hinton et al., a cooling fin is connected to the battery cell having railings for holding the cooling fin as each cooling fin slides between the railings thereby fitting the cooling fin within the respective battery cell thereby forming the aforementioned apparatus. The engagement of the cooling fin with the battery cell is presented in such a manner that the cooling fins do not extend beyond the battery cells. Thus, cooling agent only serves its intended purpose applicable if introduced from the side of the apparatus. If, for example, the cooling agent is applied to the front of the apparatus, only first battery cell is exposed to the cooling agent thereby preventing effective cooling of other battery cells.

p-0015Alluding to the above, FIG. 7 of the U.S. Pat. No. 6,821,671 to Hinton et al. shows the apparatus wherein straps are inserted through ears extending from the cooling fins to connect multiple battery cells to form the apparatus and fins together to keep the battery cells in compression. The straps, as shown in FIG. 7 deform the battery cells thereby negatively affecting chemical reaction between electrolyte, cathodes and anodes of each battery cells and resulting in a reduced life span of the cells.

p-0016The Japanese publication No. JP2001-229897 teaches a battery pack design and method of forming the same. The purpose of the method is to create the voids between the cells for cool air to go through the voids and between the cells to cool the cells. Similarly to the aforementioned U.S. Pat. No. 6,709,783 to Ogata et al., the battery pack taught by the Japanese publication No. JP2001-229897 is intended to define the voids between the cells thereby diminishing the packaging characteristics of the pack.

p-0017Therefore, there remains an opportunity to improve upon the packs of lithium batteries of the prior art to increase the ambient temperature range at which the lithium battery operates and to provide a new battery pack with improved packaging characteristics.

p-0018Also, there remains an opportunity to maintain the battery pack at the optimal operating temperature to ensure the longest possible life cycle, rated capacity, and nominal charge and discharge rates.

SUMMARY OF THE INVENTION

p-0019A battery module or pack of the present invention is adaptable to be utilized in various configurations including and not limited to a horizontally or vertically stacked battery cell packaging configurations used in an automotive vehicle. The battery pack has a plurality of battery modules each presenting a multitude of cells each sandwiched by respective heatsinks formed from thermally conductive materials such as, for example, flat stock aluminum alloy foils and the like, without limiting the scope of the present invention.

p-0020Preferably, each cell is a lithium ion cell having a first current collector and a first electrode adjacent the first current collector and a second current collector and a second electrode of charge opposite from the first electrode and adjacent the second current collector. A separator layer is positioned between the first and second electrodes with the first and second electrodes conducting electrolyte therebetween. The plurality of the first electrodes and the second electrodes are stacked and packaged into an electrical insulating envelope to form a cell. The cell packaging includes side edges and terminal ends. One terminal end includes a first bend extending therefrom in a first direction. Another terminal end includes a second bend extending therefrom in a second direction opposite from the first direction.

p-0021The heatsink includes terminal ends, and top and bottom thermal transfer edges. The top and bottom thermal transfer edges may include a plurality of fins integral with and extending from the heatsink. The fins may be cold formed and are designed to transfer heat either to or from the cells depending on application. A pair of electrically insulating spacer devices or ears are mechanically attached on each side of the heatsink. A plurality of studs are molded in to and extend from the spacer on one side of the heatsink while a spacer without the plurality of studs but with relief for a sensor occupies the opposite side to form a heatsink assembly. The cell terminals are folded over the studs in an electrical series or electrical parallel configuration. The cells are disposed between the heatsink assembly.

p-0022A plurality of flexible circuit are positioned over the studs for sensing voltage at every series connection. Integral sensors are positioned on the flexible circuit to provide temperature sensing. A nut with integral spring washer is threaded and to provide a torque over each stud for electrical conductivity and mechanical retention. Two end or compression plates are attached to the heatsink assemblies aligned with one another with the cells disposed therebetween.

p-0023At least four tie rods extend peripherally through each of the heatsink assemblies and the compression plates thereby placing the entire battery module into a compressive state to promote shorter path length for ion conduction inside the cell and improved thermal transfer of either to or from the heatsink.

p-0024A potting material, such as for example, polyurethane, polyurethane foams, silicones or epoxies, is injected into the battery module placed in a case to at least partially or fully encapsulate the battery module and the corresponding cells thereby eliminating air gaps between the cells and the case. The potting material also serves to prevent the electrode stack from shifting inside the cell packaging material during exposure to shock and vibration. The potting material also prevents the cell packaging from relaxing over time and allowing the electrolyte to settle into the base of the cell package and thus reducing the cell's electrical capacity. The potting/encapsulating material also prevents movement of the battery module within the battery pack case.

p-0025An advantage of the present invention is to provide a battery module with a very high energy density characteristic, wherein the high energy density is accomplished by assembling cells, power and data bussing devices, controllers, cooling, and retention architecture in the small volume of space thereby improving packaging characteristics and providing a compact product.

p-0026Another advantage of the present invention is to provide a battery module having excellent retention that surrounds and secures the cells.

p-0027Still another advantage of the present invention is to provide a battery module having excellent retention that surrounds and secures the electrode stack within the cell envelope from shifting.

p-0028Still another advantage of the present invention is to provide a battery module encapsulated by the potting material which greatly reduces the potential permeation of liquids into the battery pack, or leakage from inside the battery module to the outside of the battery pack thereby preventing reduced product life or premature failures of the battery module.

p-0029Still another advantage of the present invention is to provide a low mass design of a battery pack which includes polyurethane foam as a potential retention device, which is very competitive to that of traditional methods of retention, such as, for example, silicone or epoxy adhesives.

p-0030Still another advantage of the present invention is to provide a packaging method which utilizes a case that houses the module that includes a taper filled with an encapsulant which locks the module in position and will allow the pack to be mounted in any orientation.

p-0031Still another advantage of the present invention is to provide a battery pack that reduces manufacturing costs due to simplified assembly methods.

p-0032Still another advantage of the present invention is to provide a battery pack having a balanced thermal management system wherein each cell of the battery pack receives a similar temperature and flow of thermal management media to assist in the removing or adding heat.

p-0033Still another advantage of the present invention is to provide a cooling system which allows the battery pack to deliver and receive high rates of current, i.e. the C-rate by efficiently removing undesired heat during the rapid charge or discharge pulse that may negatively impact the performance and life span of the battery pack.

p-0034Still another advantage of the present invention is to provide a heating system which allows the battery pack to operate when exposed to temperatures below the optimal operating range of the cell chemistry.

p-0035Still another advantage of the present invention is to provide a pack that is simple in design and has a reduced mass.

p-0036The subject invention provides several advantages over the battery packs of the prior art by increasing an ambient temperature range at which the battery pack can operate. Also, the subject invention helps maintain the battery pack at an optimal operating temperature to extend the life cycle of the battery pack, and to increase battery pack safety.

BRIEF DESCRIPTION OF THE DRAWINGS

p-0037Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

p-0038<figref idrefs="DRAWINGS">FIG. 1</figref> is a perspective view of a battery pack containing a plurality of modules each have a plurality of cells each interconnected with one another within the battery module, additionally illustrated are battery pack control electronics and external connections;

p-0039<figref idrefs="DRAWINGS">FIG. 2</figref> is another perspective view of the battery pack of <figref idrefs="DRAWINGS">FIG. 1</figref> showing two battery modules each presenting the cells sandwiched by heatsink assemblies with each battery module supported by a base of a housing;

p-0040<figref idrefs="DRAWINGS">FIG. 3</figref> is another perspective view of the battery pack of <figref idrefs="DRAWINGS">FIG. 2</figref> showing the aforementioned two battery modules and a pair of bussing devices with stress relief members disposed on the battery modules thereby interconnecting the same;

p-0041<figref idrefs="DRAWINGS">FIG. 4</figref> illustrates a fragmental view of the battery modules interconnected by the bussing device with stress relief members presenting a stress relief element between the battery modules;

p-0042<figref idrefs="DRAWINGS">FIG. 5</figref> shows the heatsink assembly of the battery pack;

p-0043<figref idrefs="DRAWINGS">FIG. 6</figref> shows an alternative embodiment of the heatsink assembly;

p-0044<figref idrefs="DRAWINGS">FIGS. 7 through 12</figref> show fragmental views of alternative thermal transfer edge configurations;

p-0045<figref idrefs="DRAWINGS">FIG. 13</figref> shows the cell having a pair of terminal bends extending into different directions;

p-0046<figref idrefs="DRAWINGS">FIG. 14</figref> shows a partial and perspective view of the cell engaging the sensor area of the heatsink assembly;

p-0047<figref idrefs="DRAWINGS">FIG. 15</figref> shows a partial and perspective view of the cell engaging the terminal end of the heatsink assembly;

p-0048<figref idrefs="DRAWINGS">FIG. 16</figref> illustrates a perspective and partial view of the battery module showing the sides of the heatsink assembly and the heatsink thermal transfer edge extending therefrom and also illustrates the bends of the cells engaging the sides of the heatsink assembly being pressurized by a plurality of pressure plates and a rod extending through the heatsink assemblies thereby applying pressure to the cells;

p-0049<figref idrefs="DRAWINGS">FIG. 17</figref> illustrates a perspective and partial view of an alternative embodiment of the battery module;

p-0050<figref idrefs="DRAWINGS">FIG. 18</figref> a perspective view of the battery module having a flexible circuit extending over the bends of the cells and between the pressure plates and extending to a terminal tail portion to provide interconnection to a controller as best shown in <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0051<figref idrefs="DRAWINGS">FIG. 19</figref> is a perspective view of a front compression plate assembly;

p-0052<figref idrefs="DRAWINGS">FIG. 20</figref> is an alternative embodiment of the battery module shown in <figref idrefs="DRAWINGS">FIG. 1</figref>, illustrating a plurality of heating devices;

p-0053<figref idrefs="DRAWINGS">FIG. 21</figref> shows a side view of the battery module of <figref idrefs="DRAWINGS">FIG. 20</figref> disposed in a housing; and

p-0054<figref idrefs="DRAWINGS">FIG. 22</figref> shows a top view of the battery module of <figref idrefs="DRAWINGS">FIG. 20</figref> disposed in the housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

p-0055Referring to the Figures, wherein like numerals indicate like or corresponding parts, a battery unit or pack of the present invention is adaptable to be utilized in various configurations including and not limited to a horizontally or vertically stacked battery cell packaging configuration used in an automotive vehicle applications. The battery assembly or pack is generally shown at <b>10</b> in <figref idrefs="DRAWINGS">FIG. 1</figref>. The battery assembly <b>10</b> includes a plurality of battery modules, each generally shown at <b>12</b> in <figref idrefs="DRAWINGS">FIGS. 2 and 3</figref>.

p-0056Each battery module <b>12</b> includes a plurality of cells, generally indicated at <b>14</b> in <figref idrefs="DRAWINGS">FIG. 13</figref>. Preferably, each cell <b>14</b> is a lithium ion cell without limiting the scope of the present invention. Those skilled in the battery art will appreciate that other cells can be utilized with the present invention. Each cell <b>14</b> includes a plurality of battery components (not shown) co-acting between one another with electrolyte therebetween as known to those skilled in the lithium battery art. A first electrode is adjacent a first current collector and a second electrode of charge opposite from the first electrode is adjacent a second current collector. A separator layer is positioned between the first and second electrodes with the first and second electrodes with electrolyte therebetween. A plurality of first electrodes and second electrodes are stacked and packaged into an electrical insulating envelope to form a cell.

p-0057Alluding to the above, the cell <b>14</b> presents side edges <b>16</b> and <b>18</b>. A first bend <b>20</b> presents a positive terminal and a second bend <b>22</b> presents a negative terminal. Each bend <b>20</b> and <b>22</b> with a defined angle of at least ninety degrees and up to ninety degrees. Each bend <b>20</b> and <b>22</b> presents a pair of semicircular openings <b>24</b>. Alternatively, each bend <b>20</b> and <b>22</b> may present other openings (not shown). As best shown in <figref idrefs="DRAWINGS">FIGS. 13 through 15</figref>, the first bend <b>20</b> extends in an opposite direction from the second bend <b>22</b>, i.e. the openings <b>24</b> of the first bend <b>20</b> face oppositely from the openings <b>24</b> of the second bend <b>22</b>.

p-0058As best shown in <figref idrefs="DRAWINGS">FIG. 2</figref>, the battery module <b>12</b> includes a plurality of heatsink assemblies, generally shown at <b>30</b> in <figref idrefs="DRAWINGS">FIG. 5</figref>. Each heatsink assembly <b>30</b> is formed from a thermally conductive material such as aluminum, copper, and the like, without limiting the scope of the present invention. Each heatsink assembly made of a plate, sheet, or foil <b>30</b> presents a thermal transfer face <b>32</b> defining top and bottom thermal transfer edges <b>34</b> and <b>36</b> and terminal ends <b>38</b> and <b>39</b> interconnected by corners <b>42</b>. The terminal ends <b>38</b> and <b>39</b> define cut out portions <b>44</b> and <b>46</b> to receive spacers <b>48</b> and <b>50</b> formed from non-conductive polymer or non electrically conductive material without limiting the scope of the present invention. One spacer <b>48</b> includes at least two studs <b>52</b> and <b>54</b> extending therefrom to receive the cell terminal openings <b>24</b> of each bend <b>20</b> and <b>22</b>. Opposite the first spacer, the second spacer <b>50</b> includes at least a pair of concave features <b>56</b> and <b>58</b> to receive sensors (not shown) to monitor cell <b>14</b> temperatures. <figref idrefs="DRAWINGS">FIG. 6</figref> shows an alternative embodiment of the heatsink assembly, generally shown at <b>30</b>.

p-0059Alluding to the above, at least one edge of the thermally conductive plate, sheet, or foil <b>34</b> terminates to a fin portion, generally indicated at <b>60</b> in <figref idrefs="DRAWINGS">FIG. 5</figref>, presenting a corrugated configuration <b>60</b>. <figref idrefs="DRAWINGS">FIGS. 6 and 17</figref> show the fin portion <b>60</b> presenting tabs <b>62</b> being bent to a gate shape extending beyond the plate <b>32</b> as viewed from the top edge. <figref idrefs="DRAWINGS">FIGS. 7 through 12</figref> show fragmental views of alternative embodiments of the fin portion <b>60</b>. <figref idrefs="DRAWINGS">FIG. 7</figref> shows the fin portion <b>60</b> being pleated <b>64</b>. <figref idrefs="DRAWINGS">FIG. 8</figref> shows the fin portion <b>60</b> being planar <b>66</b>. <figref idrefs="DRAWINGS">FIG. 9</figref> shows the fin portion <b>60</b> having a plurality of slots or holes <b>68</b>. <figref idrefs="DRAWINGS">FIG. 10</figref> shows the fin portion <b>60</b> in the form of a bend <b>70</b> to provide a thermal interface plane for an external heating or cooling device including but not limited to heater blankets and/or cooling jackets. <figref idrefs="DRAWINGS">FIG. 11</figref> shows the fin portion <b>60</b> in the form a hook <b>72</b>. <figref idrefs="DRAWINGS">FIG. 12</figref> shows the fin portion <b>60</b> presenting the tabs <b>74</b> similar to the tabs <b>62</b> of <figref idrefs="DRAWINGS">FIG. 6</figref>, but being bent to a gate shape having a concave surface <b>76</b> extending beyond the plate <b>32</b> as viewed from the top. Those skilled in the art will appreciate that numerous other shapes of the fin portion <b>60</b> can be utilized to provide better surface area for cooling or heating media, such as liquids, solids, or gasses, and the like, are introduced to the fin portion <b>60</b> of each thermally conductive plate, sheet, or foil <b>32</b> to either cool or to heat the cells <b>14</b> of the battery module <b>12</b> without limiting the scope of the present invention.

p-0060Alluding to the above and as best illustrated in <figref idrefs="DRAWINGS">FIGS. 14 through 16</figref>, a mechanical connection between the cells <b>14</b> and the heatsink assembly <b>30</b> is generally shown. As the battery module <b>12</b> is being assembled, the heatsink assemblies <b>30</b> are oriented in such a fashion wherein the heatsink assemblies <b>30</b> are oriented in alternating fashion. In other words, the spacer <b>48</b> of one heatsink assembly <b>30</b> is alternated with the spacer <b>50</b> of another heatsink assembly <b>30</b>, as best shown in <figref idrefs="DRAWINGS">FIG. 16</figref>. Thus, the bend <b>20</b> of one of the cells <b>14</b> is connected with the bend <b>22</b> of another cell <b>14</b> with the studs <b>52</b> and <b>54</b> extending through the respective semicircular openings <b>24</b>. The bends <b>20</b> and <b>22</b> of the cells <b>14</b> are folded over the studs in an electrical series or parallel configuration. Therefore, the battery module <b>12</b>, when assembled, defines a positive side, generally indicated at <b>82</b>, and a negative side, generally indicated at <b>84</b>.

p-0061As shown in <figref idrefs="DRAWINGS">FIG. 18</figref>, a plurality of compression bars <b>86</b> having a crowned or bowed configuration are connected to the spacer <b>48</b> to apply uniform pressure across the cell terminal bends <b>20</b> and <b>22</b> interconnected with one another and to secure a flexible circuit <b>88</b> and <b>90</b> which are attached about both sides of the module <b>12</b>. Each flexible circuit <b>88</b> and <b>90</b> extend to tail portions <b>92</b> and <b>94</b> terminating into a connection port <b>96</b> and <b>98</b> to mate with the battery electronic controllers <b>100</b> and <b>102</b>.

p-0062As best illustrated in <figref idrefs="DRAWINGS">FIGS. 4</figref>, <b>15</b>, and <b>19</b>, a pair of compression plates, generally indicated at <b>104</b> and <b>106</b>, are designed to form terminal walls of each battery module <b>12</b>. A set of spaced holes <b>108</b> are defined in the compression plates <b>104</b> and <b>106</b> and also heatsink assembly <b>30</b> to receive rods <b>110</b> extending through the compression plates <b>104</b> and <b>106</b> and the heatsink assembly <b>30</b> and are secured by fasteners <b>112</b> to apply pressure to the cells <b>14</b> and to place the entire battery module <b>12</b> into a compressive state to promote a shorter path length for ionic conduction inside the cells <b>14</b> and improve heat transfer to the heatsink assembly <b>30</b>. Alternatively, each compression plate <b>104</b> and <b>106</b> present male and female features (not shown) that engage and retain adjacent heatsink assemblies <b>30</b>. As best illustrated in <figref idrefs="DRAWINGS">FIG. 5</figref>, a set of conical/countersink features <b>40</b> extend from the thermally conductive plate, sheet, or foil <b>32</b>. To aid in assembly alignment.

p-0063As best illustrated in <figref idrefs="DRAWINGS">FIGS. 3 and 4</figref>, the battery pack <b>10</b> includes a pair of conductive members <b>120</b> and <b>122</b> electrically connecting the battery modules <b>12</b> with one another. Each member <b>120</b> and <b>122</b> is defined by a flat strap, i.e. bar having a stress relief element <b>124</b> of an S-shaped configuration disposed on each member <b>120</b> and <b>122</b> for reducing stress of the battery pack <b>10</b> as the vehicle (not shown) is in motion. The number of the members <b>120</b> and <b>122</b> is not intended to limit the scope of the present invention.

p-0064As best illustrated in <figref idrefs="DRAWINGS">FIGS. 1 through 3</figref>, the battery pack <b>10</b> is assembled, it is then placed into an enclosure or housing, generally indicated at <b>130</b> The housing <b>130</b> includes a base <b>132</b> for supporting the modules <b>12</b> and a case <b>134</b> to enclose the modules <b>12</b>. The housing <b>130</b> is formed from a polymer material or non-polymer material or combination thereof without limiting the scope of the present invention. The case <b>134</b> defines a pair of spaced windows, only one is shown at <b>136</b> in <figref idrefs="DRAWINGS">FIG. 1</figref> for exposing the fin portions <b>60</b> to cooling and/or heating media introduced to the fin portions <b>60</b> through the windows <b>136</b>.

p-0065Alternatively, the use of a different fin configuration, as illustrated for example in <figref idrefs="DRAWINGS">FIG. 10</figref>, and corresponding thermal media i.e. water jacket, would not require the opening <b>136</b> on the enclosure <b>130</b>. As best shown in <figref idrefs="DRAWINGS">FIG. 1</figref>, a module retention structure partially indicated at <b>140</b>, formed from a polymer material, such as, for example, foam, injected between the modules <b>12</b> and the housing <b>130</b>. A polyurethane encapsulating solution <b>142</b> is used to secure the cells <b>14</b> and the aforementioned components within the battery pack <b>10</b>. The type of foam or encapsulant is not intended to limit the scope of the present invention.

p-0066For example, a laminar flow of a mixed two-part encapsulant is poured into the battery pack <b>10</b>. The abundance of surface area contact and excellent adhesion properties of the encapsulant <b>142</b> to the internal components provides a significant mechanical advantage of retention verses traditional methods such as RTV. The expansion of the encapsulant <b>142</b> also greatly enhances the structural integrity of the battery module <b>10</b> with respect to shock, vibration, and crush loads. The encapsulant <b>142</b> extends between each cell <b>14</b> and the heat sink assemblies <b>30</b> to encapsulate each cell <b>14</b> thereby eliminating air gaps between the cells <b>14</b> and the heat sink assembly <b>30</b>.

p-0067Heat transfer coefficients are improved due to the elimination of associated insulation layers created by dead air gaps. The encapsulant <b>142</b> shot size would be controlled not to allow it to rise over the heat sink fin configuration for air cooled applications as shown in <figref idrefs="DRAWINGS">FIGS. 1 through 3</figref>. The encapsulate <b>142</b> also serves to prevent the electrode stack from shifting inside the cell packaging material during exposure to shock and vibration. The encapsulant <b>142</b> also prevents the cell packaging from relaxing over time and allowing the electrolyte to settle into the base of the cell <b>14</b> package and thus reducing the cell <b>14</b> electrical capacity.

p-0068Referring back to <figref idrefs="DRAWINGS">FIG. 1</figref>, the pack <b>10</b> includes a pre-charge circuit <b>150</b>, a short circuit protection <b>154</b>, a current sensor <b>152</b>, a power connector <b>156</b>, a pair of power contactors <b>160</b>, and a pair of power buss bars <b>164</b> extending from each module <b>12</b> and connected to the respective power contactors <b>160</b>.

p-0069Alluding to the above, the battery pack <b>10</b> further includes temperature sensors (not shown) disposed within the housing <b>130</b> for sensing the temperature of the cells <b>14</b>. The temperature sensors are electrically connected to the flexible circuit <b>88</b> and <b>90</b> that receives the temperature from the temperature sensors and routes the data to the battery controller circuits <b>100</b> and <b>102</b>. If the temperature exceeds set safe limits, the battery controller will shut down the entire battery pack <b>10</b>.

p-0070Those skilled in the art may appreciate that the battery pack <b>10</b> may include multiple temperature sensors and multiple control circuits. In addition, the arrangement of the cells <b>14</b>, cooling devices, heaters, if required, the temperature sensors, and the control circuits may be different than as shown in Figures or described. Furthermore, one temperature sensor may be used with multiple control circuits, or each control circuit may have its own temperature sensor. Each may be controlled by the control circuit, or each heater, if required, may be controlled by separate control circuits.

p-0071Alluding to the above, <figref idrefs="DRAWINGS">FIGS. 20 through 22</figref> illustrate another alternative embodiment of the present invention, generally shown at <b>200</b> having at least one pack, generally indicated at <b>201</b>. The fin portions <b>204</b> extending from the thermal transfer edges of each heat sink assembly <b>204</b> present an L-shaped configuration defining an angle of approximately ninety degrees as, best shown in <figref idrefs="DRAWINGS">FIG. 21</figref> and earlier in <figref idrefs="DRAWINGS">FIG. 10</figref>, to form a co-planar interface surface for efficient transfer of thermal energy, generally located at <b>208</b>. Each co-planar surface <b>208</b> supports at least one heater blanket or heater device <b>210</b> having a heating element (not shown) for heating the heat sink assembly <b>204</b> which in turn heats the cells <b>14</b>. The heater <b>210</b> may be used to heat the cells <b>14</b> of the battery module <b>200</b> to an optimal operating temperature.

p-0072One skilled in the art can appreciate that a lithium ion battery may only operate optimally within an ideal temperature range. When the ambient temperature is below 0° C., the performance of the cells <b>14</b> is greatly reduced. Therefore, the heater <b>210</b> heats the battery module <b>200</b> to the optimal operating temperature, which allows the battery module <b>200</b> to be used when the ambient temperature is below 0° C. For instance, with the heater <b>210</b>, the battery module <b>200</b> may be used in ambient temperatures as low as −40° C. Those skilled in the art will appreciate that the temperatures referenced are merely given as an example. Alternatively, the heater <b>210</b> may be replaced by a water jacket devices (not shown) for cooling the co-planar interface surface <b>208</b> for introducing cooling agent such as for example liquid, gas, or solids and the like to the heat sink assembly <b>206</b> thereby cooling the cells <b>14</b>.

p-0073Various types of heaters <b>210</b> are known in the art and are within the scope of the subject invention. In a preferred embodiment, the heater <b>210</b> may be a resistor that dissipates heat into the enclosure or housing <b>212</b>.

p-0074As shown in <figref idrefs="DRAWINGS">FIGS. 20 through 22</figref>, a plurality of compression bars <b>86</b> having a crowned or bowed configuration are connected to the spacers <b>205</b> and <b>206</b> to apply uniform pressure across the bends (not shown) of the cells <b>14</b> interconnected with one another and to secure a pair of flexible circuits <b>224</b> and <b>226</b>. Each flexible circuit buss <b>224</b> and <b>226</b> extends to tail portions <b>228</b> and <b>230</b> terminating into a connection port <b>232</b> and <b>234</b> to communicate with at least one battery electronic controller <b>236</b>.

p-0075Alluding to the above, the battery module <b>200</b> further includes a temperature sensors (not shown) disposed within the enclosure <b>212</b> for sensing the temperature of the cells <b>14</b>. The temperature sensors are electrically connected to the flexible circuit <b>224</b> and <b>226</b> that receives the temperature from the temperature sensors and routes the data to the battery controller circuit <b>236</b>. If the temperature exceeds set safe limits, the battery controller will shut down the battery. The battery controller also compares the temperature to a predetermined minimum temperature using a first comparator (not shown). When the temperature in the enclosure <b>212</b> falls below the predetermined minimum temperature, a second comparator (not shown) is used to activate a transistor (not shown) that enables the heaters After the enclosure <b>212</b> has been heated to a predetermined set-point temperature, the heaters are disabled and stop heating the enclosure <b>212</b>.

p-0076Alluding to the above other advantages of the present invention are shown. The inventive battery packs <b>10</b> and <b>200</b> have very high energy density characteristics, wherein the high energy density is accomplished by assembling the cells <b>14</b>, power and data bussing devices, the controllers, thermal management, and retention architecture in the small volume of space thereby improving packaging characteristics and providing a compact product. The battery packs <b>10</b> and <b>200</b> present excellent retention methods that surrounds and secure the cells <b>14</b> and present a cost effective design of the battery module <b>12</b>. Another advantage of the present invention provides the battery packs <b>10</b> and <b>200</b> are encapsulated by the potting material, which greatly reduces the potential permeation of liquids into the battery module, or leakage from inside the battery packs <b>10</b> and <b>200</b> to the outside of the battery packs <b>10</b> and <b>200</b> thereby preventing reduced product life or premature failures of the battery packs <b>10</b> and <b>200</b>.

p-0077The inventive concept of the present invention provides other advantages over the prior art. The battery packs <b>10</b> and <b>200</b> have efficient packaging characteristics, which provide an excellent retention method that surrounds and secures the cells <b>14</b>, and the internal electrode stacks within the cells <b>14</b>. Second advantage of the present invention is unique design of the battery packs <b>10</b> and <b>200</b> having improved adhesion and surface area contact between battery cells <b>14</b> and the heatsink assembly <b>30</b> and the encapsulant disposed therebetween and material density thereby providing the battery packs <b>10</b> and <b>200</b> with the structural integrity being superior to prior art battery packs using traditional retention methods. Still another advantage of the present invention is to provide the battery packs <b>10</b> and <b>200</b> having a chemical resistant design wherein the internal components of the battery packs <b>10</b> and <b>200</b> are encapsulated by the potting material which greatly reduces the potential permeation of liquids into the battery pack <b>10</b>, or leakage from inside the battery packs <b>10</b> and <b>200</b> to the outside of the battery packs <b>10</b> and <b>200</b> thereby preventing reduced product life or premature failures of the battery packs <b>10</b> and <b>200</b>.

p-0078While the invention has been described as an example embodiment, it will be understood by those skilled in the art that various changes maybe made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.